Automatic telephony



P. A. L.. ANSPACH AUTONATIC TELEPHONY TELEPHONY 1923 5 Sheets-Sheet Fight half.

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P. A. L.. ANSPACH AUTOMATIC Filed Sept. 19,

UM `S5 mw y? La Juy T, 3925.

P. AA L. ANSPACH AUTOMATI C TELEPHONY Filed Sept. 19, 1923 5 Sheets-Sheet 5v P. A. l ANSFACH AUTOMATIC TELEPHONY Filed Sept. 19, 1923 5 Sheets-Sheet 1 Aff' H C A P S N A L A. P.

July 7, 1925.

AUTOMATTC TELEPHONY 5 Sheets-Sheet 5 Filed Sept. 19 1923 Patented July 7, 1925.

UNITED STATES PATENT OFFICE.

AUTOMATIC TELEPHONY, p

` Application led September To all whom it may concern.'

Be it known that I, Pinnnn ADRIEN LioNnL ANSPACH, a Belgian subject, residing at 38 Rue du Parnasse, Brussels, Belgium, 6 have invented certain new and useful Improvements in Automatic Telephony, of which the following is a specification.

This invention relates to automatic telephony and has for its object to provide an improved method and an improved system of circuitsI and apparatuses which allow ot simplifying considerably the operations and connections that are necessary forl establishing automatically a speaking circuit f between two subscribers and for maintaining said circuit during the 'whole time of the conversation. Among the methods that are possible in theory for the purpose of establishing a determined speaking circuit, one interesting method consists .in influencing by means of apparatuses generally known as recorders or registers, an element corresponding to thenumber of the called subscriber, and establishing a connection between this element and another element corresponding to the number of the calling subscriber and maintaining this connection until one of the subscribers hangs up his receiver again. In practice the establishing and maintenance of this connection occasion great diliculties similar by the Way to'those that stand in the way of the general use of a larger number of automatic telephone systems hitherto proposed, these diiiiculties being due mainly to the multiplicity of circuits and devices required in large exchanges for the purpose of enabling a large number of calls and conversations to take place simultaneously. The present invention provides a simple and practical solution of the whole problem and allows of eliminating the above mentioned difficulties.

According to this invention there is applied between selected elements corresponding respectively to the instruments ofthe calling and called subscribers a potential difference that is sufficient to generate between leads connected respectivel to these instruments, electrical discharges or instance in the form of sparks, arcs or silent discharges, for establishmg communication between the calling instrument and the called instrument. By

19, 1928. Serial No. 663,689;

this means a means of connection is established .which is reliable in action, can be easily controlled and requires no wipers or other mechanical devices outside of lthe necessary relays.

In addition to the establishment of the 'l N y 1,545,025lv communication by means of electrical discharge or discharges this invention has for its object to effect the selection, b means of these discharges, of the path ta en bythe communication in the network including the several subscribers instruments, and to protect by means of suitable devices the communication against all disturbing influences.

The potential diierence that feeds the discharges may be generated by any source of direct or alternating current. It is applied to the calling and called elements by recording devices composed for instance of i a series of relays that edect the preliminary 'selection To the elements that corre-y spond to the several Subscribers instruments there are `connected the branches of a network which comprise breaks or series of such breaks in such a manner that immediately the potential difference is applied between the calling and the called elements, discharges are produced at the breaks in the said branches that connect these elements to the network, and thus the desired communication will be established. 0n the other hand the relays that have efected the preliminary selection resume their state of rest immediately the called element has been im'iuenced, and they become again available for responding to fresh calls. The connectio-ns however are established in such a manner that these fresh calls cannot inliuence the instruments that have previously been placed into communication.

The communication established by the discharge between the callin element and the called element can serve directly as a speaking circuit. Nevertheless, for the purpose of obtaining a good transmission it may be preferred to substitute a new speaking circuit for the circuit that has been temporarily closed by the discharge. This substitution can be made very simply by the action of relays having their windings included in he interrupted circuit or connected to the atter.

The accompanying drawings illustrate diagrammaticall by way of example' various practical embodlments of the invention.

In these drawings:

Figure 1 shows the circuits and the apparatuses of an exchange for four subscribers.

Figure 2 is a partial view of `a network serving sixty-four subscribers.

Figures 3 and 4 illustrate simplied connections for artial networks.

Figure 5 1 ustrates another method of establishing connections between the subscribersinstruments and the partial networks.

Fi re 6 is a separate view of a cord circuit etween two subscribers instruments.

Fi re 7 is a diagrammatic view of a modification of the cord circuit.

Figures 8 and 9 illustrate in detail two constructional examples of the cord circuit shown in Figure 7 and the adjacent line circuits. v

In order to facilitate the vunderstanding of the invention an exchange for four subscribers only is shown -in Figure 1. It should however be noted right away that the complication of the connections, which is very great for this small number of subscribers, does not increase in proportion to the number of the subscribers but on the contrary, as the number of subscribers increases, it is possible to introduce simplifications as hereinafter described.

The system of connections illustrated in Figure 1 establishes the communication lin three stages namely the application by means of the selecting devices of a potential difference to the elements corresponding to the calling and called subscribers instruments, the connection of these elements by means of the electric spark, and the substitutionfor this connection of the speaking circuit proper.

The stations of the four subscribers being designated by the reference letters A, B, C and D, and their number being referred to as numbers 11, 12, 21 and 22, it is assumed that subscriber D desires to communicate with subscriberC.

The line wires 1 and 2 of each of the stations A, B, C, D at the exchange are connected to the instruments (not shown) oi' the respective subscribers in such a. manner that when subscriber D takes his receiver olf its hook, a circuit is closed through'bat# tery 3, winding 4 of the line relay a wires 5 and 2, the subscribers instrument, wire 1 and earth. Further, in addition to the winding 4, the relay a comprises a winding 6 acting in the opposite sense to 4. The relay a being energized by 4, closes the circuit'through th-e switch 7 and the switches 8V and 9.v The switch 7 closes a circuit through battery 3 winding 4, wire 10, contact 113 and earth, so that relay a is rendered self-holding, that is to say, it keeps closed of itself.

On the other hand switch 8 closes a circuit through wires 12 and 13 of station D, and through the lead 14 to which the wires 13 of all the stations are connected. This circuit is com leted through wires 13, switches S, windings 6 and batteries 3 of the stations A, B, C, since the action of the windings 6 has the etfectof locking temporarily the line relays a of these stations in their open positions in order that they shall not be influenced by calls emanating from those stations. For the purpose of preventing an abnormal locking from taking place in the case of simultaneous calls, the current which is being sent out continuously over the self-holding circuits of the line relays, will be sent out over the circuits of each subscriber (by means of a device similar to that of the insulated segments of bell machines). This device is not shown so as not to complicate the drawing uselessly.

The switch 9 places the wires 5 and 15 into circuit and thereby connects the line 1, 2 of subscriber D to a lead 16 from which the wires 15 of all the stations branch oi and which places the calling station into communication with the re isters.

For this urpose the lea 16 is connected to the winding 18 of a relay b and to a battery 20 by means of a wire 17 from which is branched o a trembler apparatus that generates an interrupted current which, through the medium of a condenser, will be perceptible to the calling subscriber. The latter is then able to know whether therecorders are disengaged.

The circuit closed bythe switch 9 will' then extend from earth to battery 2() through 1, 2, 5, 9, 15, 16, 17, 18. The relay b then operated and moves a switch 19 which closes a circuit through battery 20, resistance 23, lead 24, winding 25 of the first registering relay alL and earth. Resistance 23 is sufficiently high to cause the current, which then passes through 2.5, to be i'nsuiiicient to operate the relay d1.

On the other hand the relay b vhas likewise actuated a switch 26 which closes a circuit through the battery 20, wire 27 and winding 28 of a relay c which actuatcs in its turn switches 29 and v30. The switch 29 closes a circuit 'through battery 31, wire 32, and winding 330i the relay c in such a manner as to render the latter self-holding. Switch 30 closes one of the breaks in a circuit that includes the winding 34 of a relay 71, the action of which is hereinafter described. v

A very short time is sufficient to perform in the manner above described the o erations that are necessar for e'ecting t e automatlc closure of circuit 20, 23, 19, 24, 25 and the pre aration of the registers for their work o preliminary selection.

The registers consist lof a plurality of groups corresponding each to a numeral of the subscribers numliers to be called, and, each group comprises a plurality of sets of three relays each. Thus for 9999 subscribers, four groups (correspon-ding respectively to the thousands, hundreds, tens, `and units) of ten sets of three relays, are required. In the very simple case given by way of example, two registering groups vT and U are sufficient, each consisting of two sets of three relays d, e, f. The relays f that constitute the last term of each set, effect the selection of the element corresponding to the called subscriber, to which there will be applied b the action of a general releasing relay g t e potential difference which will create by a stream of sparks a communication between the said element and a similar element corresponding to the calling subscriber. In the illustrated example it is assumed that the mechanism by means of which the calling subscriber indicates the number of the called subscriber is of the known type comprising a rotary disc provided with a register mark which is caused to revolve over a series of divisions numbered to indicate successively the numerals of which the demanded number is composed. After each movement of the disc it is returned by a spring into its normal position, and a switch, actuated by the disc during its return movement, opens the line circuit a number of times corresponding to the numeral marked on the division at which the disc has been stopped, the last break being longer than the others, in order to mark the passage of the numeral of a certain order of magnitude (for instance the hundreds) to the numeral of the next followin order of magnitude (the tens) and to in uence the recording relays at that instant. This indicating mechanism does not form part of the present invention, and therefore, it is not thought necessary to give a more detailed description thereof.

ln order to call subscriber C having t-lie number 21, the disc must therefore be moved first opposite the numeral 2 in order to produce two breaks (a short and a long one) in the circuit during its return movement, then opposite the numeral 1 in order to produce a single long break. These breaks in the line circuit passing through 16, 17, 18, cause impulses in the wire 24. As a matter of fact at the first break, the magnet b releases its armature and the switch 19 is returned by a spring into the position shown in the drawing. The wire 24 is thereby con'- nec-ted to battery 20, not through the high resistance 23, but through the circuit 30, 35, 36, 34 whose resistance is very much less, thereby producing in the wire 24 and the winding 25 a current impulse of suiiicient strength to energize the rely b1. This impulse will not have anye ct upon relay It because the latter is of the delayed-action (slow-acting) type, and the break in the line circuit which, in the present case will produce the first impulse, will be too short to energize the relay lz.

The operation of the rela@- all places, through tue medium of the switch 40, the relay e1 into circuit with the wire 24. The relay el being energized forms a circuit from 24 to earth by way of the winding 42 of the relay d2, switch 43, and the winding 44 of relay f1. However the im ulse has ceased' and current is fed again t rough the high resistance 23 before switch 43 is closed so that the current passing through 43, 44 is too weak to energize d although it is sufiiciently strong to energize f1. The first` break in the line circuit 1, 2, 16, 18 has thus the final effect of closing aswitch 45 through f1; but this closure remains inoperative so long as the releasing relay g is not energized. It. has however the result of preparing, by the passage of a current, the operation of the relay d belonging to the next highest number by the act-ion of the complementary7 current that will be sent over the wire 24 by the following impulse.

When the first break in the line circuit ceases, the relay b places the wire 24 again into connection with the great resistance 23, but the relays all and e1 remain energized, because the current, although diminished, now fiows through the two windings 25, 46 of d1. The relay f1 also remains temporarily energized.

The second break in the line circuit produces, by closure of circuit 20, 30, 19, 24, a fresh impulse in wire 24 whose circuit is now completed by way of 42, 43 and earth. The current then'fiowing in winding 42 of the relay d2 will be sufficient to close the switch 47, wherebywire 24 will be placed into circuit with said switch 47 and the winding 48 of relay e2. This latter acts upon two switches of which one, 49, cuts ofi the current in winding 44 of relay f1, and the other 50, places into circuit the w1ndin r 51' of relay f2 which closes switch 52. Witli this arrangement of relays it will be perceived that, whatever the vnumber of impulses transmitted by the group wire 24 may be, only the lio relay f which is energized by the last impulse, will remain energized for the purpose of eectinr the selection.

It is to llos noted that in the more usual cases, where the groups contain morethan two units, the self-holding circuits 46 of the relays d1, d2, &c., can be rendered independent of wire 24 in order to avoid difculties in the adjustment of these relays. The second impulse being a long one, the delayedaction relay It has time to act and it actuates the switch 53 in such a way as to cause the line current to pass (no longer through the winding of the relay Z1 which controls the recording relays of the group T) but over the wire 54 and the coil of the relay b which controls in the san-1e way the relays of the group U. In the saine time the relay h lopens the switch 55 which interposes into the'circuit 20, 30, 35, 34, 24, 25, a resistance 56 suliiciently great to weaken any subsequent impulses in the wire 25 and prevent the relays d', cl2, etc., of the group from reacting, which would mix up the call.

The relays b, n, It and the recording relay ahr, f of the group U are disposed in the saine manner as those of the group T and the same series of operations is repeated up to the closing of the relay f reached through the last (long) impulse intended for this group. In the present example this group only receives a single impulse, and the relay f will remain energized and ,'Will maintain the switch 45 in its closed position.

When the selection of the group U has .beenl effected, the delayed-action relay It passes the connection on to the following group, or if, as in the illustrated example, U is the last recording group, the relay 71. closes, through its armature 53 a lead 54 which places the coil 58 of the releasing or uncoupling relay g into circuit with the battery 31.

The releasing relay g, as has been stated above, is intended to cause the establishment of a potential difference between an element corresponding to the station ofthe calling subscriber and an element corresponding to the station of the called subscriber. In the present case these elements are constituted on the one hand by leads 61, on the calling or transmitting side, and on the other hand by leads 62, on the called or receiving side of each station. To each lead 61 and 62 there corresponds a spark gap 63 composed essentially oi' electrodes for instance, of carbon, which may be open to the atmosphere or be placed in a vacuum tube, or a tube filled with argon or other 1nsulating gas. In the present exam )le each spark gap 63 comprises a single e ectrode facing multiple electrodes to the number of four, thc electrodes of one polarity being indicated by 64:, and those of the opposite polarity by 65. The single electrodes are connected each to the respective leads 61 and 62 of the corresponding stations, and the multiple electrodes on the calling side of each station are connected cach through a wire 66 to a multiple electrode on theV called side of each station.

Vhen the circuit 54 of the releasing relay gis closed by the armature of the relay h, the relay g opens a switch 37 and closes two switches 71 and 81.

Switch 37 opens the circuit 32 that maintained the rela c in its operative position, and thus permlts the relays b and lt to re sume their normal rest positions. It is advisable to mention here that, in practice, ally the self-holding circuits of the line relays a are under the control of an apparatus knownas a time alarm which, if the demanded communication has not been satisfied, acts after a certain delay7 to open the said selfholding circuits an to open the circuit 32 in order to return the registerin device into their normal osition. On t e other hand the periods o time necessary for the actuation of the other relays are so proportioned as to ensure that the action of a subscriber shall not last after the return of the recording devices to normal. The switch 71 closes a circuit 7 2, 73, 74, 7 5 which contains the coil 77 of the individual calling relay y,

designed to pace into circuit the lead 61 of the calling station D. Only the relay y of station D is infiucneed by the closin of the switch 71, because the coil 67 of this relay is already traversed by the current assing through the circuit 3, 4, 7, 10 closefat the start of the operations by the relay a of station D. Each relay y is re lated in such a manner that it requires t e sum of two currents passing through 67 and 77 for its energization and for permitting to attract its two armatures 78, 80 whose action is hereinafter described.

On the other hand the switch 81 closes four circuits 82, 83, 84, 85 of which each ends terminate on one hand at the battery 31 and on the other hand respectively at each of the armatures 45, 52, 45, 52 of the recording relays f. Thjese armatures cdopeiate with contacts connected in a certain order by wires 86 ot appreciable resistance, to the coils 87 of the individual receiving relays z intended to place into circuit the leads 62 when they are called. 'Ihe order in which the contacts of the armatures 45 and 52 are connected to the coils 87 is determined by the number of subscribers and the telephone number of each subscriber. In the illustrated example the relay a of station A (No. 11) will be connected to the contacts of the armatures 45 (numeral 1 ot' the tens) and 45 (numeral 1 ot the units) the relay aB (No. 12) will be connected to the contacts of -`l5 and 52, the relays C (No. 2l) to those ol'l 45" and the relay e of station D (No. 22) to those ol 52 and 52. The coils 87 are so diinensioned as not to energize the relays a except when these coils are traversed by the sum of the currents arriving through thc wires 86 conectad thereto. l

For convenience elements such as 61, 62, y, a will hereafter be referred to as 61^, 62^, g/A, zA, or 61B, etc., according as they belong to station A, B, etc. It has been explained above how, in order to call 52 and station C, the impulses given to the recording relays have closed the armatures 52 and 45, It will then be perceived that only the coil 87 of the relay eC will receive cur- Cil rent through the two wires 86 which terminate there. Consequently only the relay zc will be energized and will attract its two armatures 88 and 98.

The encrgizatiou ot' the relay y on the one hand and of the relay a0 on the other, completes the work of preliminary selection which lasts a few seconds (the time of operating the disc in order to indicate the number of the called subscriber) the operations that follow being almost instantaneous and measurable in thousandths of a second.

The relays y/D and 2C when they are energized, connect respectively through their armatures 78 and 88, the wires 61D and 62C with mains or omnibus bars 79 and 89 between which a source 90 of continuous or alternating` current maintains permanently a difference of potential. The closing of the switches 7 Sand 88 will then have for eect to apply this difference of potential to the wires 61D and 62C. Immediately the current is discharged through a spark in the spark gap 63 at the calling side of station D and in that of the called side ot station C, between the single electrode ot each of these spark gaps and those of multiple electrodes which are connected to one another through the wire 66 terminating at these two stations, so that a circuit is established between 61D and 62C through these twoI spark gaps 63 and the wire 66 connecting them. The spark thus chooses its path between the several electrodes ot the spark gaps in order to connect automatically the elements coresponding `to the calling and called stations. The circuit thus established may serve directly as a speaking circuit, hereinafter described with reference to Figues 7.` 8 and 9. in the example illustrated in Figure 1 the passage of the current in this circuit is utilized to close an independent speaking circuit which can be easily realized in the following manner. In each wire 66 are interposed in series the coils 91 of two relays m controlling each a double switch 92 which closes a break in the wires 93, 94 intended t9 be connected to the line in order to constitute the speaking circuit. The relays m operate each a switch 95 interposed in a third wire 99 that serves as a release wire.

In the wires 93, 94 of the speaking circuit there are interposed in a known manner for example a battery 100, capacities 101, 102, and impedances 103, 104, 105, 106 of which the last two serve as coils for release relays p and g which control swtiches v107, 108 interposed in the third wire 99. As soon as the relays yD and a are energized, the wire 94 is connected to:

this battery, energizes the relays p and qwhich close and take over the control eachA of a half of the third wire 99.

. The circuit formed by the wire 99 is fed through a battery 109, and its two halves contain respectively the coil 110 of the cutting-ott relay la of the calling station D and that of the called station C, and terminate at earth. As soon as the circuits constituted by the two sections ofthe wire 99 have been closed by the switches 107, 108, coils 111 interposed in this wire act upon the relays m in order to maintain these in their closed positions independently of the current passing in wire 66 and the spark gaps 63. It is to be understood that the periods of time necessary for energizing the relays that/come into operation are so determined that the flux which jumps overas a discharge and which starts the formation of the cord circuit, is not cut-ott except after the operations for assuring the maintenance of this circuit have been accomplished.

The closing of the circuits formed by the third wire 99 at the calling and calledstations establishes automatically the connection of the speaking wires 93, 94 to the line 1, 2 of each of these stations.

At the calling station` Dv the cutting-ofi relay k operates the switches 113, 114. The switch 113 opens the circuit 3, 4, 7, 10, 67 and thus causes on the one hand the release of the line relay a and on the other hand the release of the individual calling relay y. This latter permits the switch 80 to open again, but at the same time the switch 113 connects wire 94 to earth through wire 115, so that the current continues to pass through coi] 106 of the release relay q.

On the other hand the switch 114 cuts" tem T, U of the recordin relays which are thus rendered again availa )le for responding to fresh calls from the group of subscribers which they serve. This movement of the switch 114 connects the line 1, 2, to the wire 116 of the bell circuit 117 118 which includes the coil 119 of the bell relay s. This latter is immediately energized and it instantaneously opens the bell circuit through the switch 120, while through the switch 121 itcloses through the battery 122, wire 123, switch 113 and earth a circuit which includes the coil 124 of the relay s (which should remain energized) and the coil 125 of thelastaction relay r, This relay r then actuates the ist double switch 126 which connects the speakin wires 93, 94 to theline 1, 2, and switch 12 which dlsconnects the line 1, 2 to earth.

At the called station C the closing of the cutting-off relay gives rise to the same operation as at the post D with this difierence that the ringing up circuit 117, 118 remains connected to the line 1, 2 of the post C in such a manner as to cause the ringing up apparatus 128 on this line to operate until the moment when subscriber C unhooks his receiver. VBy the un'hooking of the receiver at station D, a resistance and a capacity interposed in series in the line 1, 2 have been shunt-connected in a known manner so that line current may be ysufficient in order to energize relay s when the switch 11-1 has connected the coil 116 to the line and the ringin up apparatus has not time to operate, wile at station C the current passing through 116 will not be suiicient to energize relay s, and the ringing up will continue on the line sol long as subscriber C shall not have unhooked his receiver.

When subscriber C has unhooked his receiver, communication is established. As the .line relay an is released and the recording being served by each relays are released at the moment when the cutting ofi' relay la is energized, nothing is then opposed to communication being established and to conversation taking place between the stations A and B independently of the conversation between C and D.

. When, on the conversation being finished, one of the suscribers C, D hooks up his receiver the How of current in the coils 105 and 106 of the release relays p and g is cutoi". The latter cuts-ofi the current in wire 99 which includes the cutting-oft' relay 7c which uts out of action the relays r and s and brings backthe connections into their positions of rest.

As above stated the herein described network of four subscribers is only intended to enable the working of the system according to the invention to be understood. They only indicate imperfectly on the one hand the great importance of the selective action of the spark 4and on the other hand the numerous simplifications and the great rcduction in the number of relays which becomes possible in practice when `the number of subscribers is large. The individual stations A, B, C, etc., of the latter are then classed in groups each connected to a recording system T U similar to the single recording system of Figure 1. A first simplication thus results in that a group T U of recording relays may serve for example a hundred of stations A, B, etc.. the number of individual stations capable of roup of recording relays depending on tie intensity of the traliic over the network. On the other lhand it is sufficient if the exchange is provided with two sourcesbf current, the one at low voltage which is represented in Figure 1 by batteries 3, 31, etc. battery and the other at higher voltage which is represented in Figure 1 by battery 90, butv which ma consist for example of a dynamo or an aternator and is intended to feed the omnibus bars 79 and 89. These bars can accomplish the function indicated for all the stations of the exchange, each of these stations being adapted on the one hand to influence its rela y when it operates as 4a calling station an on the other hand of being influenced by its relay z when it re,- eeives a call. l y

One of the most important simplifications concerns the reduction of the number of leads between the calling and called elements ofthe different stations, and it results from the possibility of arranging the spark gaps in series which permits of multiplying in geometrical progression the number of individual stations served by the network. Figure 2 represents theseriesarrangement of several groups or stations of partial selector networks R1, R2, RB, that is to say of elementary networks connecting two series of spark gaps, similar to the wire networks which, in Figure 1, connect the spark gaps 63 to one another. In order not to complicate Figure 2, the latter shows only the wires 66 of these partial networks, and

for greater clearness there is there indicatedv (with the exception of l ducting plate 69 is interposed between the electrodes 64 and 65 in such a way as to divide u each spark in two fractions of uni form liangth. In the spark gaps 63 the plate 69 is subdivided into two plates 69 connected to one another by the wire 68, and respectively facing the electrodes 64 and the electrodes 65. For greater clearness this figure shows only the wire 68 which comes fied by reducing the number of wires 66 which connect the sparking devices to one another. Thus, for example, these wires 66 which are to the number of 16 in the network of four subscribers illustrated in Figure 1, can be reduced to the number of eight when they are connected two by two, for example as in Figure 3, or even to the number of four as in Figure 1, the wires 66 then having common points or sections 66. Other sim lifications of the same kind can obviouslyv e designed in order to reduce or to increase the number of circuits according to requirements.

It has been assumed up to the present that each station is connected by its lead. 61 or 62 to a different spark gap, but there may be an advantage in connecting several spark gaps to several stations, as in the example of Figure 5 where five spark gaps 63 forming part of the same partial network are connectedto the wire 61 of five subscribers stations.

In a complete system of networks composed of partial networks, the spark will choose in the spark gaps which it meets, that path which presents the least resistance among the aths which are offered to it. It is known 1n fact that under suitable conditions, a spark of high potential follows a single path, and that, even if several paths in parallel are offered to it no harmful divisions of useful iux will be caused. The invention utilizes this henomenon, for it is desirable that the spar will be able to choose from among several aths ending at the same stations, so that i a spark gap is already occupied, the spark can pass through a spark gap located in an alternative path.` With this object there may be connected in series with the net-work, one or several sets of partial net-works more than the number strictly necessary, as determined by the number of subscribers stations, or even the partial networks or some of them may be constituted by a number of leads greater than the number strictly necessary, as determined by the number of electrodes. It is thus possible to multiply according to requirements the number of paths presented to the passage of the spark between two stations.

Protective. arrangements are provided on the one hand Jfor preventing a spark gap or a section already occupied from being influenced by a spark resulting from another call, and on the other hand for protecting the relays interposed in the conductors 66 against the high voltages proceeding from the omnibus bars. These arrangelnents are indicated on Fig. 6 which represents the cord circuit. between the stations of any two subscribers P and Q, of the net-work comprising two sets of partial net-works in series. Let us suppose that subscriber P has called subscriber Q and that the individual calling and receiving relays v/P and 2Q have attracted their respective armatures 78 and 88 in the manner previously indicated. The vo-ltagcof the source of current 90 being applied through the omnibus bars 79 and S9 to the leads 61P and 62, a current will pass through the wires 61, 66, 68, 66, 62,' jumping over in the form of sparks, the spark gaps 63, 63', 63', 63, which, in the. present example, are supposed to be connected in parallel to several subscribers stations. In order to avoid the objection that this intense current might deteriorate the relays m serving for the establishment of the speaking circuit 93, 9%, or that great precautions for insulation should have to be taken, the coil 91 of each of these relays is mounted in shunt on a non-inductive resistance 130 interposed in the circuit established between the leads 61 and 62. As the coil 91 has a strong self-induction, the current impulse which gives rise to the spark will pass through the resistances 130. This impulse is of very short duration, being limited to some thousandths ot' a second after the closing of the relays y and whose action is rendered simultaneous by a device which, in order to avoid complications, is not represented in the drawing. As soon as the discharge is started by the current impulse from the source 90, this impulse is replaced by a weaker current, of a potential insufiicient to start the discharge, but sufficient to maintain it. This current is furnished by a battery 31 and leads 131, 132 connected respectively to the leads 61 through wires 133, 134. T his low voltage current passes through the coils 91 and energizesthe relays m whose armatures 92 closel thespeaking circuit 93, 94 while the armature 95 forms t-he circuit 99 of the third wirel in which is interposed the coil 111 explained above.' A protection for the relays m can obviously be effected in another way, for example bvsubst-ituting capacities for the non-inductive resistances 130. Strong impedances 141, 142 protect the battery 31 against the high-voltage current. from the source 90. l

In order that. while the circuit of conversation 93, 94 between the posts P and Q remains closed, the spark gaps 63, 63 should not be able to be influenced by calls coming from other posts, to which these. spark gaps are connected, recourse is had to an arranfrement such as the following: In place o a conducting plate 69, the spark gaps 63 are furnished with two plates 69 connected by a wire 70 in which is interposed a' switch 135 which, normally. remains closed. This switch is controlled by a relay o whose coil 136 forms part of a circuit 137 which is fed by the battery 138 and is normally maintained open by a switch 139 controlled by one of the relays m. When the relays m are set going, that is to say during the duration tery a, yilof the corres ending local circuit of the telephonie communication between P and Q, the circuits 137 are closed and the relays 0 maintain the switches 135 in their open positions in such a way that no spark can any longer pass through the spark gaps 63. The spark gaps 63 in the same way are prevented from allowing a spark to pass through the action of switch 140 interposed in the Wire 68 and controlled by the relay g whose coil 106 remains excited during the whole duration of the communication between the stations P and Q.

A protection of occupation such as 'that described above has to be realized throughout where several paths have common points. Thus when several wires 66 `have as on Figures 3 and 4, a common point or section such as 66', this latter, immediately the communication is established, will be cut by a protective arrangement during the duration of this comn'lunication, in order to prevent the deleterious intervention of another communication.

It has been stated above that the circuit in the `wires 66 established bv the passage of the discharge in the spark gaps 63 can serve directly as a circuit of conversation. In this case the cord circuit will only comprise one conductor in place of four, the return being made by an omnibus bar, but itA is advisable to apply to it different modilications, as indicated in Fig. 7, which is a diagrammaticrepresentation of the essential elements of a cord circuit of this kind.

After the preliminary selection the lines 1, 2 of the calling subscriber P and of the called'subscriber Q are connected, as will be explained later, to the primary windings 144 of telephone repeaters mi, Q,whose secondaries 145 are in circuit with the wires 66 and the spark gaps 63 and with an omnibus bar of conversation 146 connected to the earth. At the same time the calling relay y/P and receiving relay 2Q apply the dill'erence of potential ot' the bars 79, 89 to the wires 61 and 62 of the two subscribers which end, as previously, at the first and at the last spark gap 63.

On each spark gap 63 and on each common section 66', is branched oli` a local circuit 149 normally interrupted at the interval of sparking, and containing an individual battery cz, 6, y etc.

At the moment when the difference of potential of the bars 79, 89 is applied to the wires 61p and 62Q, the discharge traverses the spark gaps, the intervals or' sparking are transformed into conductor links and the communication is established between the lines 1, 2 of the two subscribers. This difference of potential is only applied during a very short time determined by the action of the releasing relay g, and it is immediately replaced in each spark gap by the voltage of the batwhich, alt ough insuicient to start the discharge, is suliicient to maintain it, in such a way that the discharge here affects the form of a sustained arc. The local circuits situated at the two extremities cf the cord are provided with two batteries a and m of which one (a) is placed in play with the wiie 61 ou the side of the calling subscriber and the other (e) with the wire 62 on the side of the called subscriber.

At the are branc ed off on the cord circuit there are found so called cord supervising relays t provided with two coils 143, 143 interposed respectively in the adjacent circuits As soon as the circuits 149 are closed by the passage of the discharge, the relays t are set going and each cut a short circuit (not indicated on Fig. 7) which was maintained on a condenser' 14T. These condeusers constitute, during the duration ot the communication, an obstacle to the passage of disturbing discharges,l but they freely allow the vocal currents to pass. The impedances constituted by the coils of the relays t will prevent on the other hand the vocal currents trom passing through the batteries a, 6, y. The protection of the end batteries c and can be completed through impedances 187, 188.

Ink order'to better understand the operations which produce the establishment and the cutting of the communication in this circuit reference will be made to Fig. 8 which represents the line circuit of the calling subscriber P and the cord circuit ending in the line circuit of the subscriber Q.

The line Wire 1 of each subscriber is connected in a permanent manner to an extremity of the winding 144 of its repeater a'. This winding is divided, in known manner into two sections by a con-denser 148.

When the subscriber P unhooks his receiver a circuit is closed from the battery 3 through the switch 150, the rotating commutator 151 (of known type comprising a turning member 152 successively sweeping contacts 153 each connected to one of the stations of the group), the wire 154, the coil of the line relay a., the switch 155, the line 2, the circuit formed by the telephonie apparatus of the subscriber P (not represented), the line 1, the contact 127 and the earth.

The relay a acts and attracts its armature 156 which cuts the wire 154 in 157 and substitutes therefor a wire 158 which also comes from the battery 3 and contains the coil of a relay i. This relay attracts its armature 150 which cuts the communication between the battery 3 and the switch 151 and momentarily prevents any interference by the other subscribers of the group. On the other hand, through its amnature 159, the relay a substitutes for the connection to the earth laces where the local circuits 149 I.

trincea passing through the line 2, l a connection to the earth through a wire 160 and a switch 161 controlled by a so called cutting and supervising relay K and a time alarm arran ement not indicated. Finally through its armature 7 the relay a connects to the earth the coil 77 of the calling relay y, while through its armature 9, it connects the line 1, 2 to the wire 15 which, as on Fig. 1, leads to the recording apparatus.

The preliminary selection is continued in the recording apparatuses as on Fig. 1 and terminates through the action of the releasin relay g which sends current on the one hand through the Wire 72 in the coil 77 of the calling relay y of the calling subscriber and on the other hand through the wires 86 in the coil 87 of the receiving relay z of the called subscriber. Further the relay g cuts the communication of the coil of the relay a to the earth through a switch (not represented) Which successively liberates the relays a and z'. 1

At the caller, the relay y attracts its arma* tures 78, 162, 163 and 164 and at the called the relay e attracts its armatures 88 and 165. The contacts 78 (caller) and 82 (called) apply 'to the wires 61 and 62 on both sides of the cord circuit the diii'erence of potential of the bars 79, 89, while the other contacts bring in on the calling side and on the called side the relays K and S which connect the line wires 2 ot' two subscribers respectively to the primaries 144 of repeaters .rf anda/JQ, in the following man* ner.

.The contacts 162 and 165 form at the caller land at the called, a circuit from battery tery 172 to the earth through the coil 173 and the armature 163 in such a Way that the relay y1 will be self-holding during the whole duration of the communication. Through its armature 174, K cuts at the caller the connection between the bars 79, 89 and the wires 61P and 629. Through its armature 176, K connects to the wires 61 the secondaries 145 of the repeaters w? and m9. Finally through its armature 155, K connects the line 1, 2 to the source 128 of alternating ringingup current, through the contact 179, the coil 180 of the relay S, and the contact 181.

The line 1, 2 being closed at the calling station, the relay S acts; its coil 18() is immediately connected on the one hand to a 122, 166, 170 of self hold of the relay K takes earth through the line 1, 2, the wire 183, and the second coil 164 of K. Finally.

through it's armature 179, S connects the line wire 2 to the primary 154 of the repeater wf.

At the called' station the ringing-u will function until the subscriber unhoo his receiver and thus closes his line 1, 2 which immediately causes to operate his relay S which, as at the callers station, connects the line wire 2, to the primary of the repeaters m9.

While the primaries 144 of the bobhins XP and xQ are placed in circuit with the lines 1, 2 of the two subscribers, the circuit of the secondaries 145 and of the wires 66 is closed, at the intervals of sparking, through the passage of the discharge started through the voltage of the bars 79, 89 and maintained by that of the batteries as, 6,- y u. The relay y1 having attracted its armature 164, the local circuit 149 which is nearest to the calling station will be vfedv by the battery a, while the local circuit 149 which is nearest to the called station will be fed by the battery o. v l

In order to prevent the spark gaps 63 and the sections 66 common to several ramiiications from being able to be influenced by other communications when they are already occupied, there is interposed in the wires 68 between the sparking plates 69 and in the common sections 66', protective devices 190 with which are also combined members intended to act at the moment of the release of the circuits at the end of the conversation, and of which the principal elements are the condensers 147 and the relays t of supervision of the cord. For the simplicity of the drawing there has only been represented in detail on Fig. 8 one of the devices190.

When the passage ot the arc has transformed the intervals of sparking into conductor links, the relay t, excited by its twov coils, acts andpitsarmature 191 cuts a short circuit which it maintains, at rest, on the condenser 147 which will form from this time an obstacle to the passage of a new discharge. Through its armature 192, t prepares the establishment of a circuit containing the coils 193, 194 of two relays fa and fw which will intervene at the time of ,i the release of the circuits at the end of the.

communication. During the conversation the vocal currents, of high frequency, freely pass through the condenser 147.

The release of the circuits is produced When one of the subscribers hooks up his receiver. In cutting the line 1, 2 he cuts the circuit of self-hold of the ielay K which releases its armatures, of which one, 171 Cuts the Circuit of self-hold of the relay s which, in its turn releases its armatures. But during the very short time which separates the release of K and that of S, the alternating current of the source 122 1s applied on the cord through the contact 185,

i the Wire 186, the contact 176 and the Wire 61 and` finds earth at the subscribenwhich has not yet been hooked up. It 1s this momentary alternating current vvhich, in the arrangement represented in Fig. 8, Will canse the opening of the local circuits formed by the passage of the discharge.

In the arrangements 190 the alternatlng current (which is of much lower frequency than the vocal currents) passes through the coil 195 of the relay 'w and the condenser 196 which are branched otl' on the condenser 147 .l The relay w acting, constitutes a circuit ot self-hold ofv the battery 195 to the earth through the contact 198. the coil 194, the

contact 192 and the coil 193 of the relay v This last cuts, through its armature 199, the adjacent local circuit 149-, and the arc is put out in the corresponding spark gap. The relay t also comes back to rest and cuts. at 192 the circuit of the coils of 'v and fw which are released in their turn. The release is produced in each local circuit, in such a ivay that the coid circuit, like the line circuits, is again in state of establishing a new communication.

Figure 9 represents another lconstructional example of the invention which ditl'ers from the preceding, principally by the manner in which is eli'ected the release of the circuits after the end of the conversation. Instead of being caused by the emission of an alternating current at the moment when the first of the subscribers hooks up his apparatus, the release of the cord circuit is produced by the release of a relay L Whose coil 200, interposed in the Wire 61, is fed at the caller by the battery a. and at the called by the battery ci. The coil 200 is connected to the circuit 149 of the batteries oa and e) through two conductors 201, 202 in parallel, 0f which one contains the switch 203 which is closed by the action of the relay K and the other contains the switch 204 which is opened through the setting into action of the relay S. The relay L here controls the armature 171 which governs the circuit of selthold of the relay i/ and the armature 174 which cuts the connection between the bar 79 and the Wire 61. W'hen a call is issued, the relays a, K and S function as in Fig. 8

and the relay L is set going from the time of the passage of the discharge in the cord circuit. i

The cord circuit comprises as previously, protective devices 190 for the spark aps 65 and for the common sections 66', ut by their arrangement these devices differ in l,

through its armature 206, the connectionA between the coil 143 of t and its associated battery (y for the device 190 represented in detail in Fig. 9), but a connection in parallel has been formed through an armature 207 of the relay t. It follows that through the play of the armatures 206 and 207, the battery y will be connected to the relay zthrough one path or the other, except at the moment When t releases its armature 207, the subsequent closing of 20G being only produced with a slight delay.

Then one of the subscribers hooks up his receiver, the relays K and S are successively released, but during the brief interval of time which separates their return to the position of rest the two switches 203 and 204 are open. The local circuit 149 containing the coil 200 of the relay L and the battery a (or (o) is then cut, and the relay t of this circuit is released, for the constant of the relays t is such that they ought to be excited by tivo coils in order tobe or to remain set in action. The arc is put out, and the opening of the local circuits 149 spreads gradually nearer and nearer throughout the icord until all the elements have ietalren their positions of rest.

There is only represented on Figs. 8 and 9, a single cord circuit. but it is easily understood that if there is considered the representation of a network such as that of Fig. 2, each of the batteries a, 6, y Q can serve to feed the partial circuits of all the spark gaps or of all the common sections of the same order, represented in a same vertical alignment on Fig. 2.

In the foregoing there has been indicated by the term spark gap the devices traversed4 by the discharge. It should be understood that this term broadly covers devices of any appropriate type, Whether they operate in free air or in an enclosed vessel, and Whether the discharge be in the form of sparks, of arcs, of emanations or in general of any passage of Huid across a nonconducling or a bad conducting medium permitting of establishing as communication or of effecting a selection between the ill,

attacca branches of an interrupted network. It should further n be understood that these means of connection and selection can be combined with arrangements of preliminary selection oi' an type Whatever and in general, that modiiications can be made to the systems described without departing from the spirit of the invention.

I claim l. In a method of automatically establishing a telephonie connection, applying a potential difference to selected elements respectively corresponding to the calling and called stations, and causing electric discharges to select a path in an interrupted network to connect. said elements with one another.

2. VIn a method of automatically establishing a telephonie connection, applying a potential difference to selected elements respectively corresponding to the calling and called stations, causing electric discharges to connect said elements with one another, maintaining said discharges for the dura tion of the call, and utilizing said discharges for the transmission of speakin currents.

3. In a method of automatica l establishing a telephonie connection, app ying a potential diii'crence to selected elements respectively corresponding to the calling and called stations, causing electric discharges initiated by said potential difference to connect said elements with one another', substituting for the said potential difference a lower potential dilierence for feeding said electric discharges, and utilizing said discharges for the transmission of speaking currents.

Ll. In a method of automatically establish ing a telephonie connection, applying a potential difference to selected elements respectively corresponding to the calling and called stations, causing electric discharges initiated b said potential difference to select a patli in an interrupted network to connect said elements with one another, substituting for the said potential diderence a lower potential difference tor maintaining said electric discharges, utilizing said discharges for the transmission of speaking currents, and causing said discharges to cease upon either of the subscribers ending the call.

5. In an automatic telephone system, the combination of elements respectively corresponding to each subscribers station, a network interposed between said elements, spark gaps in said network, means operative during the building up of a call for selecting two of said elements, and means for connecting said two elements with each other through said network by producing electric discharges across selected spark gaps in said network.

6. In an automatic telephone system, the

combination of calling elements and receivf, ing elements both respectively corresponding to each subscribers station, a network intern posed between said calling elements and said receiving elements, spark gaps 1n said network, means operative during the build-1 calling and receiving elements, a source of' current, and means operatlve during the building up of a call for causing a selected individual calling relay and a selected individual receiving relay to connect said source of current with said network through the calling and receiving elements respectively corres ending to said selected rela s, the potentia of said source ot' current ieing suticient to produce electric discharges in said spark gaps.

8. In an automatic telephone system, the

combination of a plurality of elements, a network interposed between said elements, f

said network comprising a plurality ot partial selective networks, spark gaps in Said network, each ,spark gap being connected to a plurality of said partial networks, means operative during the building up of a call for selecting two of `said elements, and means for producing electric discharges across selected spark gaps in said network to connect said selected elements with each other.

9. In an automatic telephone system, the combination of a plurality of elements a network interposed between said elements, said network comprising a plurality of sets of` partial selective networks arranged in series, spark gaps in said network, each spark gap being connected to a plurality of partial networks of the same set, means operative during the building up of a call for selecting two of said elements, and means for producing electric discharges across selected spark gaps in said network to connect said selected elements with each other.

10. In an automatic telephone system, the combination of a plurality of elements, a

network interposed between` said elements, g5

said network comprising a plurality of sets of partial selective network arranged in series, each partial network comprising a plurality of branches connected together to form common sections, spark gaps in said net# work, each spark gap being connected to a'.

plurality of partial networks of the same set, means operative during the building up ot a call :tor selecting two oi said elements, and means for connecting said selected elements with each other through said network by producing electric discharges acrossselected spark gaps in said network.

ll. In an automatic telephone s stem, the combination of a plurality of eements, a network interposed between said elements, said network comprising a plurality ot sets ot partial selective networks arranged in series, spark gaps in said network, said spark gaps comprising a plurality ot' electrodes ot each polarityand atleast one conducting member extending between the electrodes of opposite polarities, the electrodes ot' opposite polarities being connected to partial networks of different sets. means operative during the building up of a call tor selecting two of said elements, and means for connecting said selected elements with each other through said network by producing electric discharges across selected spark gaps in said network.

12. In an automatic telephone system, the

.combination ot a plurality of elements, a

network interposed between said elements, spark gaps in vsaid network, means operative during the building up of a call for selecting two of said elements, means l'or producing electric discharges across selected spark gaps in said network to connect said selected elements with each other, and protecting means 't'or preventing an engaged spark gap -from being influenced by a discharge resulting from another call.

13. In an automatic telephone system, the combination of a plurality of elements, a network interposed between said elements, said network comprising a plurality ot' partial selective networks, said partial networks comprising a plurality of branches having common sections, spark gaps connected to the branches oit` said partial networks, means operative duringthe building up ot' a call for selecting two ot said elements, means for producing electric discharges across selected spark gaps to connect said selected elements with each other, protecting means for preventing an engaged spark gap Jfrom being influenced by a discharge resulting from another call, and protecting means for preventing an engaged common section from being influenced by a discharge resulting from another call.

ist. In an automatic telephone system, the combination of a. plurality oil elen'ients. a network interposed between said elements, spark gaps in said network, a source ol current of sullicicnt potential to initiate electric discharges in said spark gaps, a source ot current of lower potential suliicient to sustain previously initiated electric discharges in said spark gaps, means operative during the ot' said lilies, a network interposed between.

said elements, spark gaps in said network, a source ol current of suleient potential to initiate electric discharges in said spark gaps, a .source oi' current of lower potential sullicient to sustain previouslyv initiated electric discharges in said spark gaps, means operative during the building up ot' a call for selecting two ot' said elements, means for connecting the first mentioned source of current to said network through said selected elements, means vtor substituting the second mentioned source ot current for the first mentioned source of current, and means for inductively connecting said selected elements to their corresponding lines respectively.

1G. In combination with the parts recited in claim la, means for disconnecting the second mentioned source of current from said network ou the call being ended.

17. .ln combination with the parts recited in claim l5, means Vt'or disconnecting the second source ot current 'from said network, and means for disconnecting said selected elei'nents from their respective lines, both said disconnecting mea-ns being adapted to operate on the call being ended.

18. In an automatic telephone system, the combination of a plurality of elements, a network connected to said elements, spark gaps in said network separating said elements from one another, means operative during the building up of a call for selecting two of said elements, means for setting up a connection between said selected elements through selected spark gaps of said network, means for maintaining said connection, and means for causing said connection to be broke at said selected spark gaps on the call being ended.

19. In an automatic telephone system, the combination ot' a network, spark gaps in said network, means for producing electric discharges across selected spark gaps, and means for causimr said discharges t0 transmit vocal currents across said selected spark gaps. l

20. In an automatic telephone system, the con'ibination ot' a network, spark gaps in said network, a source of comparatively high potential adapted to produce electric discharges across said spark gaps, sources of comparatively low potential adapted to maintain discharges produced in said spark ncaacae gaps, means for causing said source of high potential to produce discharges in selected spark gaps, means for causing said sources ot' low potential to maintain said discharges in each of said selected spark gaps, and means for causing said maintained discharges to transmit vocal currents across said selected spark gaps. e

Q1. In an automatic telephone system, the combination of a network, spark gaps in said network, means operative during the building up of a call for producing electric discharges across selected spark gaps, means :tor preventing said selected spark gaps from bcing influenced by another call, and means ior causing said discharges to transmit vocal current across said selected spark gaps.

22. ln an automatic telephone system, the combination of a network, spark aps in said network, means operative during the building np of a call for producing electric discharges in said selected spark gaps, means for causing said discharges to transmit vocal currents across said selected spark gaps, condensers in said network, and means controlled by said maintaining means for inserting said condensers in the path of said vocal currents.

23. ln an automatic telephone system, the combination of a network, spark gaps in said network, means operative during the building up of a call for producing electric discharges across selected spark gaps, means for maintaining said discharges, said maintaining means comprising local circuits ccnnected to said spark gaps and sources of current in said circuits :tor feeding said discharges, relays controlling each one of said local circuits, each relay having two windings respectively comprised in the local circuit controlled thereby and in the adjacent local circuit, means for causing said discharges to transmit vocal currents across said selected spark gaps, and means ttor causing said relays to successively break said local circuits on the call being ended.

24. ln an automatic telephone system, the combination of a network comprising successive sets of a plurality of branches, the branches of each set being connected to common sections, spark gaps in said network having their opposite electrodes connected tov branches of dilterent sets, means operative during the building up o a call for charges to transmit vocal currents through selected branches and across said selected spark gaps, a plurality of condensers, and means for inserting selected condensers in the common sections connected to said selected branches and between the opposite electrodes of said selected spark gaps.

25. ln an automatic telephone system, the combination of a pair of electric conductors, a spark gap having its opposite electrodes respectively connected to said conductors, a pair of conducting members interposed between the opposite electrodes of said spark gap, a connection between said conductin members, a pair of sources of current, eacli of said sources ot current being connected to one of said electric conductors and to the connection between said conducting members, a condenser` a relay having two windings, one in circuit with each source of'current, said relay being adapted, when energized, to insert. said condenser in the connection between said conducting members, and means operative when said relay is de-energized for momentarily disconnect# ing one of the windings of said relay Jfrom the source of current in circuit therewith.

26. In an automatic telephone system, the network comprising a succession of conductors, spark gaps interposed between successive conductors, local circuits branched each on one of said spark gaps, means for producing electric discharges across said spark gaps, and means in each of said local circuits for feeding said discharges.

27. In an automatic telephone system, a network comprising a succession of partial networks, spark gaps interposed between successive partial networks, local circuits branched each on one of said spark gaps, means responsive to a call Jfor producing electric discharges across selected spark gaps, Y

and means for causing said discharges to transmit vocal currents, said local circuits including each means for feeding said discharges, means for protecting engaged spark gaps against the influence of perturbing calls, and means for momentarily breaking said circuits upon a call being ended.

ln testimony whereof` l aflix my signature.

MERRY, DRlEN lLlNEl. ANSPCH. 

